Pregnancy is ten months long in Japan!

In Japan they say that pregnancy is ten months long. We say its nine months long in Europe. I spent my whole life thinking a term of pregnancy is nine months long and when you do the math; it is! There is no dispute that the average pregnancy is 40 weeks long. By European calculations that is about 9.2 months. However, in Japan, due to the lunar calendar, they take the view that a month is 28 days or four weeks long, hence 40 divided by four is ten months.  

However, only one month of the year has exactly four weeks and that is February (except in a leap year). And if you calculate it by days, a pregnancy on average is about 280 days. Given that a month has an average of 30.4 days and divide 280 by 30.4 to get the months, that's 9.2 months. Also, if you calculate by when conceives and then gives birth, it is most often 9 not 10 months after. If someone conceives in January, they will most likely give birth in October. That is nine months later.

I find it very interesting that in Japan pregnancy is considered to be ten months long. I was curious as to whether there were other countries that pregnancy is said to be ten months long and it turns out that other countries who are also still influenced by the lunar calendar, seem to also say ten months. They include South Korea, China and Vietnam. How about in your country - do they say nine or ten months?